Oral mucosa shows marked variation in structure which appears to be related to regional differences in function. A similar pattern of variation is seen in the skin. Epithelia are continuously regenerating structures and there is evidence to suggest that subepithelial connective tissues may exert both facilitating and modulating influences which maintain regional specificity of structure in adult epithelia. Many of the adverse pathological processes occurring in the oral cavity, ranging from periodontal disease to carcinoma are associated with, or are causally related to, changes in the maintenance of epithelial structure and information which loads to an understanding of this process would be of great value. As working hypotheses we postulate that a) epithelial histodifferentiation, as characterized by patterns of keratin synthesis, rates of cell division and establishment of tissue architecture is continuously modulated by the subepithelial connective tissue and b) such adult epithelial patterns can be remodulated. The objectives of the propposed research are to evaluate whether a ) the differences in patterns of epithelial protein synthesis are dependent on a connective tissue influence b) connective tissue structure affects epithelial behavior c) differential cell attachment is related to the variable facilitating abilities of different connective tissues d) epithelial proliferation is influenced by the connective tissues e) such tissue interactions are similar to interactions occurring during embryonic development. These problems will be investigated using a selected range of oral epithelial and epidermal specimens, either homo- or hetero-typically recombined with various connective tissue components, as intact sheets or as cell suspensions, which are maintained in protected in vivo sites prepared in histocompatible mice. Recombinants will be examined to determine the effects of tissue interchanges on morphological structure, rates of cell production and patterns of keratin synthesis.